The present invention relates to strut-type synchronizers for manual transmissions and, more particularly, to such a synchronizer mechanism incorporating an improved strut spring adapted for retracting and centering the blocker ring.
Strut-type synchronizers, such disclosed in U.S. Pat. No. 4,566,568 issued Jan. 28, 1986 to Yant, are used in manually operated transmission and transfer cases and generally include a plurality of spring-biased struts that are radially interposed between a driven clutch hub and a clutch sleeve. A spring member operates to radially outwardly bias the struts so as to seat the struts in a detent groove formed in the inner bore of the clutch sleeve.
As is known, axial displacement of the clutch sleeve causes the struts to act on a blocker ring for energizing the synchronizer mechanism to block further axial displacement of the clutch sleeve until speed synchronization is complete. More particularly, energization of the synchronizer mechanism causes frictional engagement between mating conical surfaces formed on the blocker ring and a ratio gear for generating sufficient torque to "clock" the blocker ring to an indexed position and rotatably drive the ratio gear. Synchronization is achieved when the relative speed between the blocker ring and ratio gear approaches zero. Thereafter, the spring member is compressed radially inwardly for allowing the clutch sleeve to pass over the struts. In this manner, internal spline teeth formed on the clutch sleeve are permitted to meshingly engage external spline teeth formed on the ratio gear for transmitting power (i.e. drive torque) from the main shaft to the ratio gear.
A primary design constraint associated with many cone-type synchronizer mechanisms is their inability to be completely "de-energized" upon disengaging the clutch sleeve from the ratio gear upon returning the synchronizer mechanism to a "neutral" position. More particularly, residual friction remaining between the mating cone surface of the ratio gear and the blocker ring may detrimentally effect the wear and life characteristics of the synchronizer mechanism. In addition, the residual viscous drag may also cause the synchronizer mechanism to "self-energize" when it is in the "neutral" position.